This invention relates to water heaters, and more particularly to direct contact water heaters.
Direct contact water heaters, such as that disclosed in U.S. Pat. No. 4,275,708 comprise a vertically oriented cylindrical column having a plurality of heat exchange bodies disposed adjacent its upper end. A spray nozzle is disposed above the heat exchange bodies for spraying the water to be heated downwardly onto the heat exchange bodies. A gas burner extends through an opening in the column and below the heat exchange bodies, for injecting a flame radially inwardly toward the axis of the column. The hot gasses from the flame pass upwardly through the heat exchange bodies in the column for discharge while the water to be heated flows downwardly over the heat exchange bodies and through the flame.
Some prior art direct contact water heaters have realized less than desired efficiencies. In particular, the contact between the water and the flame and the impingement of the flame on the relatively cool wall of the column on the side opposite the burner tends to result in incomplete combustion. This not only adversely effects efficiency, but also tends to produce aldehydes which are highly toxic.
In another type of prior art direct contact water heater, as disclosed in U.S. Pat. No. 3,648,682, the flame is confined to an open bottomed combustion chamber. While this prevents direct contact between the flame and the water being heated, the combustion chamber also tends to restrict flame length.